I've just ordered an uno and other bits and bobs, and I'm trying to figure out my power needs for a mini water pump. I've read that the Uno has a 5V output pin, and I've equally found a small USB powered water pump on amazon (DC 3.5V -9V 3W USB Submersible Water Pump).
Is the Uno powerful enough to run its self, as well as this mini water pump?
I also understand that the uno can be powered by USB or an ac to dc 12v power adapter, would this make any difference? My rationale is that the 12v will be stepped down to a level which the arduino can run on, so the rest is wasted?
You need a transistor to control the water pump power. The arduino can control the transistor.
AOI514, AOI516, AOI518 would all work well. Attached picture shows NPN, but use N-channel MOSFET instead. ~55 cents at digikey.
Uno can run from USB - use a cell phone charger if you don't plan to have a PC around.
Use a 2nd for the pump. Then you can use a higher voltage if needed to power the pump.
I also understand that the uno can be powered by USB or an ac to dc 12v power adapter, would this make any difference? My rationale is that the 12v will be stepped down to a level which the arduino can run on, so the rest is wasted?
Yes. The Arduino has a 5V voltage regulator on the board. It's a linear regulator so power is wasted. i.e. With 10V into the regulator you'd have 5V "dropped" across the regulator and the regulator will dissipate/consume the same amount of power the Arduino is consuming. (Half the power is wasted.) But, if the pump-power doesn't pass-through the regulator, none of the pump-power power is wasted.
That could be a problem if you are running off a battery but otherwise it's not a lot of wasted power and it's no big deal.
If you are running your pump from 9V, then you can run the Arduino from the same 9V power source.
"Switching" voltage regulators can be nearly 100% efficient. With a normal (step-down) switching regulator, the voltage coming-out is less than the voltage going-in, but you get more current out that what flows-in. Power (Watts) is calculated as voltage X current and a 100% efficient voltage regulator (if such a thing existed) would have the same amount of power going-in and coming-out with the voltage regulator itself consuming no power.
The Arduino contains a tiny regulator that can provide its 5V requirement up to a few hundred mA, from a voltage of about 7 to 12V. It is limited by the heat it generates in the process, and being a linear regulator, that heat is the product of the voltage it drops which is the difference between the input and 5V, and the current drawn, so the more current you draw, the less voltage it can drop before it automatically shuts itself down. It is therefore recommended that you power it from no more than 9V, and that only if you are not drawing significant current from the 5V output of the regulator.
If you power the Arduino from a USB port on a computer, the port can supply up to 500 mA and you can draw much of that from the 5V pin. The Arduino contains an overload protector to shut down if more than 500 mA is continuously drawn.
Now, your pump motor. 3W at 5V is 600 mA. You cannot in any configuration power this from the 5V pin on the Arduino. You have to provide a separate power source of the voltage range to suit the pump. You control the pump using a suitably rated NPN transistor in the negative line of the pump, with its emitter connected to the common ground of the Arduino and that pump supply. A BD135-BD137 should do the job, with a 220 ohm base resistor from the Arduino output.
Sounds like you need a 9V switchmode power adapter to power the pump and feed the Arduino Vin.
Thank you Paul, Doug and CrossRoads for your help && explanations. You really all went out your way to help me out here and I really appreciate your detailed explanations.
It all makes much more sense and I can't thank you enough :+)
FYI, if you're new, and not familiar with forum protocol, the way a poster thanks a person (or persons) who post helpful advice is to click on their "Add karma" button. This increments their karma count and adds to their credibility, similar in a way to the "****" you may have seen on some websites where people post feedback about others. You can view a poster's karma count by clicking on their avatar. It will only increment once per 24 hours for click. If they are providing ongoing assistance for a long and detailed project, you could click their "Add Karma" button every time they provide new and helpful advice. You could say it provides incentive for posters to help other posters but as you will eventually come to realize, the people doing most of the helping are doing it for the satisfaction of knowing they make someone's day, and not for the karma clicks. Some posters will rarely offer criticism because it may result in their "getting stiffed" (as they say) by the poster. Others will always tell you when you have screwed up (either in your documentation , or your wiring , or your nomenclature or schematic because they know that is what you really need to hear at that moment. Some posters take offense to the criticism because they think we are like paid customer service reps who are trained to operate with the attitude that "the customer's always right". Here on the forum, if you're wrong, it won't take long for you to find out. There was one guy who clicked the "Report to Moderator" button 4 times in a post that only had 28 Replies until the Senior Moderator finally posted a message to the guy that he didn't need to report "every reply" because he had been reading them all and in his opinion , none of the comments were offensive and all of the posters were trying to prevent the complainant from damaging their arduino. That was funny. (I was one of the people reported by the way. Guilty as charged .
I'm planning a quite similar project, using a mini submersible pump (Voltage :2.5-6V, Current: 130mA-220mA). As far as I understood, in this case I can use the Arduino 5v Out (because it's less than 500mA)?
If not, I also ordered a power adapter (from 1,5 to 12v, 1000mA). Could I use it to power both the Arduino and the pump? If that's the case, how should I wire it?
Thanks a lot!
Florian
Paul__B:
Sounds like you need a 9V switchmode power adapter to power the pump and feed the Arduino Vin.
The maximum current draw for the entire arduino is about 500 -700mA.
The maximum current any one output can deliver is about 30mA.
Anything that draws more than that needs to be driven with a relay, transistor or mosfet.
I also ordered a power adapter (from 1,5 to 12v, 1000mA)
The power adaptor can serve as a load power supply. If the load power supply is anything OTHER than 5V,
you would need to use the external dc barreljack if you want to use it to power the arduino in addition to the load. The external dc power barreljack can accept 7V to 11V dc. Running it with less will likely result in less than 5V on the board. Using more than 12V will overheat the regulator , which can source a maximum of about 800mA.
a mini submersible pump (Voltage :2.5-6V, Current: 130mA-220mA
You can power the pump from the arduino 5V pin if and only if you use a relay, transistor or mosfet to turn it on and off. (unless you plan to have it on all the time).
It is never a good idea to run a motor from the 5V pin of an Arduino.
Your right. The motor spikes would probably wreak havoc with the logic circuits. It is probably best to use the external supply with the voltage switch set to 5V.
There was one guy who clicked the "Report to Moderator" button 4 times in a post that only had 28 Replies until the Senior Moderator finally posted a message to the guy that he didn't need to report "every reply" because he had been reading them all and in his opinion , none of the comments were offensive and all of the posters were trying to prevent the complainant from damaging their arduino. That was funny.